Air Transport World

Loran-C may realize its potential at last. (FAA may approve for airport approaches)

The C-47 taxied to the ramp after landing in weather well below the remote airport's usual minimums. The mildly surprised observers couldn't see the black box in the cockpit that had made the landing possible despite the absence of precision approach aids on the ground.

Was this a startling new advance in avionics? No, just a 40-year-old navigation system called Loran guiding a 40-year-old airplane.

Inexpensive, accurate and proven, Loran was developed originally for ocean navigation. Now the advancements embodied in today's Loran-C cause its avaiation proponents to envision the day when commuter and regional airliners can shoot IFR approaches to any airport, on-site navigational aids or no, guided through the murk solely by one of these powerful black boxes.

Present Loran-C systems blend an innovative combination of computer memory and space-age navigation receiver technology unthought of when the first Loran-A chains were installed during World War II. Scattered mostly along coastal regions, the Loran-A transmitters (like their Loran-C counterparts) broadcast a hyperbola of very powerful low-frequency radio signals. Ships--and aircraft--used the signals and gulku vacuum-tube radios to naviagte across the vast ocean distances.

Loran--short for "long-range navigation aid"--found widespread use in maritime applications after the war. In the 1970s, technological improvements led to Loran-C, and when the large, power-hungry transmitters and receivers started shrinking in size and electrical demand, Loran-C began appearning in the cockpits of general aviation aircraft.

Today, according to avionics industry estimates, between 15,000 and 20,000 units ply the skies, providing pilots with navigational capabilities often promoted as the foreunner of satellite navigation. …

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